The Fourth Element Halo 3D undergarment has body-mapped insulation, strategically placed to enhance protection when in horizontal trim - this maximizes thermal protection, whilst minimizing buoyancy and bulk. Using a combination of cutting edge Spacetek fabric and layers of high density fleece, this is the warmest undergarment in Fourth Element's range. Designed for use underneath membrane and trilaminate dry suits. The one piece design is simple and functional; lower profile around the hips and midriff, allowing high manoeuvrability with panels of additional thermal protection layers located where they are needed most, enhancing the thermal protection in critical zones without excessive bulk. It can be worn as part of a layer system with Xerothermbase layer and in extreme cases, even fourth element Arctic undergarments. Convenient zipped sleeve pocket, full length, double headed zip with internal and external zip cover, thumb loops to aid donning, secure foot stirrups to prevent legs riding up, machine washable and quick drying.